Experimental Investigation of Natural Frequency of a Cantilever Composite Beam using Vibration Absorber

Abstract :

Composite materials are used in utmost all aspects of the industry and commercial fields such as in
aircraft, ships, common vehicles, etc. The most attractive properties of such materials include high strength-toweight
ratio and high stiffness-to weight ratio. In this paper, a composite cantilever beam specimen of size 300 x
25 x 2.5 (mm) is prepared by natural fiber material (sisal) and it is used as a basic prototype for a number of
complex flexible engineering structures which is highly resonant in characteristic. If the amplitude of vibration of
a cantilever beam becomes excessively large, ultimately the system tends to fail. To eliminate such vibrations, a
spring mass system is attached with vibration absorber to control the structural resonance. This problem is
solved by Finite Element Method using ANSYS. Then the FEM results are verified by conducting experiment. Using
FEM, the excitation is given to the beam the amplitude response without absorber is found by harmonic analysis.
Then the absorber is attached at different locations on the beam, the absorber stiffness is varied until the
amplitude of vibration in the beam is reduced to minimum. Then the beam is excited by the electro-dynamics
shaker and the amount of vibration is measured using accelerometer. The output from the accelerometer is in
analog form which is then converted into digital signal by means of data acquisition system. The circuits are
constructed by Lab VIEW software to convert the digital signal into amplitude of vibration. Finally the
experimental results were compared with FEM results for validation. Experimental results are found to be close
agreement with FEM results.